Freezed (immutable) support with 0 id fails due to assignment to final id

In #229, the example supporting freezed entities uses assignable ids. Since freezed demands entities to be immutable, attempts to use value 0 ids fail in https://github.com/objectbox/objectbox-dart/blob/e587529f3a32ce7769e9a53a24ea4afafdd6d970/objectbox/lib/src/native/box.dart#L222 with error

Unhandled Exception: Invalid argument(s): Field Model.id is read-only (final or getter-only) and it was declared to be self-assigned. However, the currently inserted object (.id=0) doesn't match the inserted ID (ID 1). You must assign an ID before calling [box.put()].

Is it possible to use non-assignable ids with immutable entities currently? If not, would it be beneficial to make it so, e.g. by modifying the code above to use a copyWith or some other mechanism to set newly assigned ids?

Start with objectbox/lib/src/native/box.dart around line 222 and compare the immutable Freezed example from issue #229. Reproduce the failure with an entity whose id is 0 and is final, then determine whether immutable entities can receive newly assigned IDs without mutation. Done means the supported behavior and its tests clearly cover this case.